package com.guw.TestReflection;


import java.lang.annotation.*;
import java.lang.reflect.Field;

//练习反射操作注解
public class Test04 {

    public static void main(String[] args) throws Exception {
        //获得class
        Class c1 = Class.forName("com.guw.TestReflection.Students");
        //通过反射获得注解
        Annotation[] annotations = c1.getAnnotations();
        for (Annotation annotation : annotations) {
            System.out.println(annotation);
        }
        //获得注解的value值
        //通过getAnnotation()获得注解,然后强转成TableSQL
        TableSQL tableSQL = (TableSQL)c1.getAnnotation(TableSQL.class);
        //获得tableSQL的value值
        String value = tableSQL.value();
        System.out.println(value);

        //获得类指定的注解
        Field field = c1.getDeclaredField("name");
        FieldSQL annotation = field.getAnnotation(FieldSQL.class);
        System.out.println(annotation.colName());
        System.out.println(annotation.type());
        System.out.println(annotation.length());
    }
}

//类名的注解
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@interface TableSQL{
    String value();
}

//属性的注解
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface FieldSQL{
    String colName();
    String type();
    int length();
}

@TableSQL("db_student")
class Students{
    @FieldSQL(colName = "db_id",type = "int",length = 10)
    private int id;
    @FieldSQL(colName = "db_age",type = "int",length = 10)
    private int age;
    @FieldSQL(colName = "db_name",type = "varchar",length = 3)
    private String name;



    public Students() {
    }

    public Students(int id, int age, String name) {
        this.id = id;
        this.age = age;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Students{" +
                "id=" + id +
                ", age=" + age +
                ", name='" + name + '\'' +
                '}';
    }
}